Rotary-piston engine

ABSTRACT

The engine comprises a four-lobe cavity and a rotor having three heads which are each maintained in contact with the stator so as to define three variable-volume chambers between the internal surface of the stator and the external surface of the rotor. An oval-shaped eccentric is rigidly fixed to an output shaft having an axis which coincides with the center of the stator and is continuously applied at three points in tangential contact with a closed track having the shape of a curvilinear triangle.

United States Patent. 1191 Leroy et al.

[ Sept. 25, 1973 ROTARY-PISTON ENGINE [76] Inventors: Marcel Leroy; Albert Thiebaut; both of 126 boulevard dAlsace Lorraine, Le Perreux, France 22 Filed: July l3, 1972 21 Appl. No.: 271,393

[30] Foreign Application Priorityv Data July 16, 1971 France 7126132 [52] US. Cl. 123/845, 418/61, 123/841 51 Int. c1.'..... F02b 55/02, 0215 55/14, F010 1/02 [58] Field of Search....;..;- 123/845; 418/61, 418/54 [56] References Cited UNITED STATES PATENTS 3,221,715 12/1965 Romoli 123/8.45 3,364,907 1/1968 Jeanson l.'... 418/61 3,426,525

2/1969 Rubin 418/61 1 FOREIGN PATENTS OR APPLICATIONS 103,413 6/1899 Germany ..123/8.01

Primary ExaminerCarlton R. Croyle Assistant Examiner-Louis T. Casaregoh Attorney--Camer0n, Kerkam, Sutton, Stowell and Stowell [5 7] ABSTRACT The engine, comprises a four-lobe cavity and a rotor having three heads which are each maintained in contact with the stator so as to define three variablevolumc chambers between the internal surface of the stator and the external surface of the rotor.

An oval-shaped eccentric is rigidly fixed to an output shaft havingan axis which coincides with the center of the stator and is continuously applied at three points in tangential contact with a closed track having theshape of a curvilinear triangle.

10 Claims, 13 Drawing Figures PATENTED 8EP25|975 SHEET 6 OF 7 1 ROTARY-PISTON ENGINE This invention relates to the technique of rotarypiston engines and more specifically engines of the type comprising a stator having a four-lobe cavity and a rotor with three heads which is capable of moving within said'cavity in such a manner as to define three variable-volume work chambers which are delimited by the internal surface of the stator and the external surface of the rotor. An engine of this type is naturally provided in addition with conventional means for admitting a gas into these chambers, for initiating the combustion process and discharging gases after combustion and expansion.

In spite of the many advantages offered by engines of this type, they have not led to any industrial development up to the present time. The maindifficulty arises at the level of the connection to be made between the rotor and an output shaft driven by said rotor.

- The use of a simple circular eccentric can'notbe contemplated for the purpose of effecting the connection just mentioned. A design solution of this type can prove satisfactory only if it is possible to provide compensation for the variable play which necessarily appears between the path permitted by a circular eccentric and the path which is in fact followed by the center of the rotor, namely a cusped, curvilinear square having the shape of an ace of diamonds.

It has therefore been proposed to make use. of a toothed pinion rigidly fixed to the output shaft and meshing with toothed racks which are rigidly fixed to the rotor and conform on this latter to the shape of a ,curvilinear triangle corresponding to the curve described by the trace of the stator on the rotor during the displacements of this latter. t

In either case, these design solutions suffer from a large number of defects. The defects which are common to both are mainly related to the impossibility of ensuring correct balancing of the rotor and the fact that the rotor heads are violently applied 'in succession against the walls of the stator and even strike these latter sharply at the bottom of the lobes.

The essential aim of the present invention is to overcome these disadvantages while retaining the advantages of rotary-piston engines of the typehereinabove defined.

To this end, the invention proposes a rotary-piston engine comprising a stator which defines a cavity having four identical lobes and a rotor which is capable of motion within said cavity and has three identical heads such that each head remains in contact with the stator so as to define three chambers having a variable volume between the internal surface of the stator and the external surface of the rotor, characterized in that the rotor has a closed track in the shape of a curvilinear triangle which contains the center of the rotor and the sides of which are parallel to those of the curve described by the trace of the stator on the rotor. during the displacements of said rotor and that said engine comprises aneccentric rigidly fixed to an output shaft having an axis which coincides with said center of the stator and driven by said rotor track, said eccentric being of oval shape in order that it should always remain in tangential contact with said track at three points.

According to one aspect of the invention, the eccentric comprises two symmetrical rollers which bear on said track and the axis of one roller coincides with the center of the stator. In a preferred embodiment of the invention, at least one first curvilinear square roller rotates about the crank-pin of the eccentric with an external surface which slides continuously over a central zone of the rotor track, at least one second curvilinear square roller'is stationary and concentric with the stator with an external surface which continuously slides over a peripheral zone of the rotor track, said peripheral zone being adjacent to said central zone.

In the engine in accordance with the invention, the displacements of the rotor are controlled by means of the eccentric which is in cooperating relation with the rotor track. It is thus possible to ensure uniform trans mission of rotational motion to the output shaft and to prevent abrupt impacts of the rotor against the stator. At zero velocity, the heads of the rotor reach their center of rotation.

A further advantage lies in the fact that the track can be formed by a hollowed portion having a cross-section in the shape of a curvilinear triangle and formed through the rotor, said hollowed portion being intended to provide a passageway for the output shaft or for an element associated with said shaft.

The last-mentioned advantage is turned to particularly useful account in one alternative embodiment of the invention in which the engine comprises two similar stator and rotor assemblies, the rotors being connected by means of a common shaft which passes through these latter and is rigidly fixed to the corresponding eccentrics.

Transfer ducts are advantageously provided for connecting the intake ports for the admission of gas into the stator cavityof a first assembly to exhaust ports for discharging gas from the stator cavity of the second assembly so that this latter accordingly constitutes a gassuction unit for supplying the first assembly which constitutes the driving unit.

The invention relates to exemplified examples which are described with reference to the accompanying drawings, wherein:

FIG. 1 illustrates diagrammatically a rotary-piston engine in accordance with the invention and as designed for operation in a four-stroke cycle and shows in particular different positions of the eccentric with respect to the rotor;

FIGS. 2 to 7 show diagrammatically different successive positions of the rotor within the stator in order to illustrate the operation of the engine;

FIG. 8 is a partial transverse sectional view of an alternative embodiment of the engine in accordance with the invention, in which provision is made for two stator and rotor assemblies;

FIG. 9 is a transverse sectional view of the three essential elements of the engine according to FIG. 8 together with the system of connections between the two assemblies;

FIG. 10 shows the outline of the eccentric of the engine of FIG. 1;

FIGS. 11 and 12 are diagrammatic views of an alternative embodiment of the invention;

FIG. 13 is a view in sectional elevation showing a preferred embodiment of the rotary-piston engine in accordance with the invention.

The rotary-piston engine which is illustrated in FIG. 1 is essentially made up of a fixed stator l and a rotor 2 which is capable of motion inside a cavity-formed within the stator.

The stator 1 possesses symmetry of revolution of quaternary order about the fixed center C, the stator cavity being designed to form four identical lobes such as the lobe la. The rotor 2 possesses symmetry of revolution of ternary order and forms three identical heads such as the head 2a which are adapted to come into position successively within each lobe of the stator.

Furthermore, the internal outline of the stator and the external outline of the rotor are so determined that at least two heads remain continuously in contact with the stator wall. Three chambers, the volume of which varies during the displacements of the rotor, are thus defined between the internal surface of the stator and the external surface of the rotor.

The shapes adopted respectively for the lobes 1a of the stator 1 and for the heads 2a of the rotor 2 determine within the stator four lobe centers 11, 12, 13 and 14 each corresponding to an instantaneous center of rotation for the rotor head 2a which is present therein. In consequence, the outline of the lateral faces of the stator lobes corresponds to circular arcs which are centered at these points. The rotor heads are each limited by two circular arcs centered at a point such as 21 which, when the head is located at the bottom of a lobe, coincides with the center 11, 12, 13 or 14 of said lobe these two circular arcs meet at a point which is fitted with packing seals and maintains a contact with the stator wall at the level of the cusp between the faces of two adjacent lobes.

Since the engine described is designed for operation in a four-stroke cycle, provision is also made for two spark plugs 31 and 32 within opposite lobes of the stator cavity and for two devices 33 and 34, each device being intended to effect the opening and closure of a duct for the admission, of gas into the cavity and of an exhaust duct. These different elements are arranged as illustrated in FIG. 1.

So far as concerns the relative positions of the stator and the rotor, the operation of an engine of this type is known per se but will nevertheless be summarized hereinafter with reference to FIGS. 2 to 7 which illustrate the successive positions of the rotor.

In FIG. 2, there begins the admission of gas into one of the chambers (on the right-hand side of the figure) up to the position illustrated in FIG. 3. The gas is then transferred to the top portion of the stator cavity up to the position illustrated in FIG. 4, whereupon the compression of this gas begins to take place. In FIG. 5, the compression has been completed and ignition takes place. Expansion of the gases forces the rotor to the position illustrated in FIG. 6. Discharge of the burned gases begins in the position of FIG. 6 and continues in the position of FIG. 7 until the rotor returns to the position which was already illustrated in FIG. 3.

Each of the FIGS. 2 to 7 shows how the displacements of the rotor consist of a series of successive pivotal movements in which the centers of rotation employed are the centers of the stator lobes 14 (FIG. 2), 13 (FIG. 3), 12 (FIG. 4), and 11 (FIG. In the case of each variable-volume work chamber, a complete cycle of operations as described in the foregoing requires six successive pivotal rotor movements. The work chamber which is limited by a predetermined face of the rotor therefore makes use in alternate succession of the ignition produced by each spark plug 31 and 32. Each of the three work chambers is subjected to the one chamber to the other.

Thus, the admission or induction takes place on the right-hand side in FIG. 2 on a first face of the rotor, on the left-hand side in FIG. 4 on a second face and on the right-hand side in FIG. 6 on the third face.

Reference will now be made again to FIG. 1. The movements of the rotor 2 which were described earlier are transmitted to an output shaft the axis of which coincides with the center C of the stator, by means of an eccentric 40. This eccentric is rigidly fixed to a shaft 3 which is not illustrated in FIG. 1 but can be seen in the general view of FIG. 13.

. The eccentric 40 is located within the interior of a hollowed portion at the center of the rotor 2 limited by a track 41 having the shape of a curvilinear triangle. The eccentric 40 (shown in FIG. 1) has an oval shape in order that three points 44a, 44b and 44c of said eccentric should be continuously maintained in tangential contact with the track 41.

The eccentric 40 is partially limited at the two opposite extremities by two symmetrical rollers 42 and 43, the roller 42 having its axis at the center C and the roller 43 having its axis at a center M. In order that friction may be reduced to an even greater extent, the sides of the eccentric can also be fitted with elements such as roller-bearings or ball-bearings. Similarly, in order to reduce the friction which is set up as the rotor heads are applied against the stator wall at the bottom of the lobes, the stator is provided, for example, with two reaction wheels 44 and 45 which are placed opposite to the two spark plugs.

The outline of the track 41 is defined on the basis of a parent track 46 formed by three equal circular arcs having as centers the three rotor-head centers such as 21 and representing the curve described on the rotor by the center C of the stator during the different movements of the rotor. The sides of the curvilinear triangle which define the track 41 are parallel to these three circular arcs and located externally of the parent track 46 at a distance which is equal to the radius of the roller 42.

The shape of the eccentric 40 is determined by the shape of the track 41. In particular, the distance be tween the centers of the two identical rollers 42 and 43 is equal to the height of the curvilinear triangles which form the parent track 46. The sides of the eccentric are of convex shape in order that this latter may be perm itted to relay the rollers 42 and 43 in providing a bearing point on the track 41. The eccentric unit as a whole is always in tangential contact with said track at three points.

As shown in FIG. 10, the outline of the oval-shaped envelope of the eccentric 40 is determined by two sets of concave curves 65-66 and 67-68 which are symmetrical and opposite in pairs and joined tangentially to each other. The two curves 65 and 66 correspond to the circumference of each roller 42 and 43 with respective centers C and M and a radius equal to the distance between each side of the parent track 46 which is parallel to the track 41 (shown in FIG. 1).

The second set of curves 67 and 68 represents the loci of the successive points of contact (44a to 44b, as shown in FIG. 1) between the track 41 of the rotor 2 and the envelope of the eccentric 40 at the time of their respective displacements.

ter 11.

through these latter.

FIG. 1 shows in chain-dottedlines three successive positions of the rotor heads, of the track 41 and of the eccentric 40 as these latter rotate about the center C during a pivotal movement of the rotor about the cen- In an alternative embodiment which is illustrated in FIGS. and 9 and designed for operation in a twostroke cycle, the engine comprises two stator and rotor assemblies 50 and'51 which are similar to the assembly the assembly 51 and in the assembly 50 for a gas-intake port and an exhaust port on each of the four faces of the stator. I g

The different exhaust ports of the assembly51 are connected respectively to the different intake ports of the assembly 50 by means of transfer ducts 54 in the manner which is illustrated in FIG. 9.

It is thus apparent that the assembly 50 constitutes a driving unit for effecting the rotation of the output shaft and, at the same time, the assembly 51 which is driven by the output shaft can serve as a gas-suction unit for supplying the driving unit. In this case, each phase of reduction in volume .of a work chamber of the assembly 51 no longer produces compression but causes transfer of gas towards one of the chambers of the assembly 50, whereupon the gas subsequently undergoes the different phases of compression, ignition, expansion and exhaust within the assembly 50.

As shown in FIG. 8, valves such as the valves 55 and 56 in the driving assembly 50 serve to open or close re- (shown in FIG. 13) in the'case just mentioned, the eccentric 40 of FIG. 1 is double (40a and 40b) and arranged on each sideof the rotor 2. The axis of revolution of the shaft 3 of the crankshaft unit 142 coincides with the center C of the stator 1 (FIG. 1).

In the example of the crankshaft unit 142 (shown in FIG. 13), the journals 3a and 3b of the shaft 3 are joined to the crank-pin 143 by means of two crankarms which form eccentrics 40a, 40b. The journals 3a and 3b are rotatably mounted in bearings 4a and 4b and the crank-pin 143 serves as a spindle for a square roller 5 having curvilinear faces or sides. Irrespective of the position of the crankshaft unit 142, the periphery of spectively the gas-intake ports and the gas-exhaust ports. Said valves are controlled by a system of tappets and rockerarms which are displaced by a distributor 57 rigidly fixed to the output shaft 53 during the rotation of this latter. Recourse is hadto a different solution in order to effect the opening and closure of the intake portsfor admission of gas into the chambers of the assembly 51 (FIG. 8). The exhaust ports of this assembly do not need to be closed since the transfer ducts are opened or closed according to the positions of the valves 55 of the assembly 50. A gas distributor 58 is mounted against the stator 51b of the assembly 51. Said distributor is provided with ducts 59 which are located opposite to the ducts 60 for admitting gas into the assembly 51 and, on the other hand, with an annular passageway 61 which is continuously supplied with gas and is provided with openings opposite to the ducts 59. However, said openingsare closed-off by a rotary disc 62. Said disc has a slot 63 which periodically establishes a communication between the ducts 59 and the passageway 61 during the time which is necessary for the admission each eccentric 40, 40a retains three points of contact with the track 41 of the rotor 2. The roller 5 is in contact with the internal track 41 either by means of one side 5a (as shownin FIG.'11) or by means of two sides 5a and 5b (as shown in FIG. 12), depending on the relative positions of the crankshaft unit and of the track just mentioned. The curvilinear square profile of a roller of the type designated by the reference 5 has the advantage of distributing the radial loads over a surface, namely the surfaces of one or two sides of the roller whereas, in the case of a roller 42 or 43 of circular shape, the radial load was applied at single points.

In order that single-point loads onthe side oppsoite to the roller 5 may also be eliminated, at least one square roller 6 (shown in FIG. 1 l) or 6a (shown in FIG. 13) having curvilinear sides is fixed-concentrically with the axis C on one radial face 7a of the stator (as shown in FIGS. 11 and 13), thediagonal axes of said roller 6 being displaced by 45 with respect to'the diagonal axes of the roller 5. Since the crankshaft unit 142 is symmetrical, it is an advantage to fix a second roller 6b which is identical with the first on the other radial face 7b of the stator. The two rollers 5 and 6 have the same orientation with respect to the axis C and bear on the peripheral zones of the rotor 2, namely the zones adjacent to the central zone against which the roller 5 is applied. In consequence, the eccentric or eccentrics 40a and 40b continue to guide the movements of the rotor 2 and the radial loads are transferred and distributed over the curvilinear sides of. the rollers 5 and 6a, 6b.

It is readily apparent that the invention is not limited to the particular embodiments which have been described in the foregoing by way of example. On the I contrary, the invention extends to all alternative forms and 43 of the eccentric 40 are of circular shape and are which come within the definition of equivalent mechanical means and especially in industrial applications such as pumps and compressors, for example.

What we claim is:

l. A rotary-piston engine comprising a stator which defines a cavity having four identical lobes and a rotor which is capable of motion within said cavity and has three identical heads such as each head remains in contact with the stator so as to define three chambers having a variable volume between the internal surface of the stator and the external surface of the rotor, wherein the rotor has a closed track in the shape of a curvilinear triangle which contains the center of the rotor and the sides of which are parallel to those of the curve described by the center of thestator on the rotor during the displacements of said rotor, and wherein said engine comprises an eccentric rigidly fixed to an output shaft having an axis which coincides with said center of the stator and driven by said rotor track, said eccentric being of oval shape in order that it should always remain in tangential contact with said track at three points.

2. An engine according to claim 1, wherein said eccentric compriese two symmetrical rollers which bear on said track and the axis of one roller coincides with the center of the stator.

3. An engine according to claim 2, wherein said rollers are cylindrical.

4. An engine according to claim 1, wherein said eccentric comprises at least one curvilinear square roller which is rotatably mounted on the crank-pin of the eccentric and the external surface of which slides continuously over a central zone of the rotor track, at least one second curvilinear square roller which is stationary and concentric with the center of the stator and the external surface of which slides continuously over a peripheral zone of the rotor track, said peripheral zone being adjacent to said central zone.

5. An engine according to claim 4, wherein said curvilinear square rollers are oriented with respect to the rotor track in such manner that the respective diagonal axes thereof are relatively displaced by an angle of 45.

6. An engine according to claim l, wherein said engine comprises two similar stator and rotor assemblies, the rotors being connected by means of a common shaft which passes therethrough and is rigidly fixed to the corresponding eccentrics.

7. engine according to claim 1, wherein said engine comprises transfer ducts which connect the intake ports for the admission of gas into the stator cavity of a first assembly aforesaid to exhaust ports for discharging gas from the stator cavity of the second assembly aforesaid so that said second assembly constitutes a gas-suction unit for supplying said first assembly which constitutes the driving unit.

8. An engine according to claim 6, wherein said first assembly is provided with four spark plugs for ignition of the gas within the four stator lobes respectively.

9. An engine according to claim 6, wherein said second assembly is provided with gas intake ducts and with a rotary slotted disc for alternately connecting said ducts to a common annular supply passageway.

10. An eccentric provided in particular for an engine according to claim 1, wherein said eccentric has an oval-shaped envelopedelimited by the junction of two sets of two concave curves which are symmetrical and opposite in pairs, the first set of curves having two centers, namely a center C of rotation of the eccentric and a center M of the crank-pin, the second set of curves being such as to represent the loci of the successive points of contact between the rotor track and said envelope. 

1. A rotary-piston engine comprising a stator which defines a cavity having four identical lobes and a rotor which is capable of motion within said cavity and has three identical heads such as each head remains in contact with the stator so as to define three chambers having a variable volume between the internal surface of the stator and the external surface of the rotor, wherein the rotor has a closed track in the shape of a curvilinear triangle which contains the center of the rotor and the sides of which are parallel to those of the curve described by the center of the stator on the rotor during the displacements of said rotor, and wherein said engine comprises an eccentric rigidly fixed to an output shaft having an axis which coincides with said center of the stator and driven by said rotor track, said eccentric being of oval shape in order that it should always remain in tangential contact with said track at three points.
 2. An engine according to claim 1, wherein said eccentric compriese two symmetrical rollers which bear on said track and the axis of one roller coincides with the center of the stator.
 3. An engine according to claim 2, wherein said rollers are cylindrical.
 4. An engine according to claim 1, wherein said eccentric comprises at least one curvilinear square roller which is rotatably mounted on the crank-pin of the eccentric and the external surface of which slides continuously over a central zone of the rotor track, at least one second curvilinear square roller which is stationary and concentric with the center of the stator and the external surface of which slides continuously over a peripheral zone of the rotor track, said peripheral zone being adjacent to said central zone.
 5. An engine according to claim 4, wherein said curvilinear square rollers are oriented with respect to the rotor track in such manner that the respective diagonal axes thereof are relatively displaced by an angle of 45*.
 6. An engine according to claim 1, wherein said engine comprises two similar stator and rotor assemblies, the rotors being connected by means of a common shaft which passes therethrough and is rigidly fixed to the corresponding 45*
 7. An engine according to claim 1, wherein said engine comprises transfer ducts which connect the intake ports for the admission of gas into the stator cavity of a first assembly aforesaid to exhaust ports for discharging gas from the stator cavity of the second assembly aforesaid so that said second assembly constitutes a gas-suction unit for supplying said first assembly which constitutes the driving unit.
 8. An engine according to claim 6, wherein said first assembly is provided with four spark plugs for ignition of the gas within the four stator lobes respectively.
 9. An engine according to claim 6, wherein said second assembly is provided with gas intake ducts and with a rotary slotted disc for alternately connecting said ducts to a common annular supply passageway.
 10. An eccentric provided in particular for an engine according to claim 1, wherein said eccentric has an oval-shaped envelope delimited by the junction of two sets of two concave curves which are symmetrical and opposite in pairs, the first set of curves having two centers, namely a center C of rotation of the eccentric and a center M of the crank-pin, the second set of curves being such as to represent the loci of the successive points of contact between the rotor track and said envelope. 